Compensating device for grinding machines



June 9, 1959 w. F. JESSUP ET AL 2, 8 5

COMPENSATING DEVICE FOR GRINDING MACHINES Filed Oct. 7, 1957 4Sheets-Sheet l IN V EN TORS.

0 W/LBUR F. JESSUP I GEORGE L.GROV Fi ,2: mw

flT'TORNEYS.

June 9, 1959 w. F. JESSUP ET AL COMPENSATING DEVI 4 Sheets-Sheet 2 FiledOct. 7, 1957 3N L U $h h ow m. Q \h mm m? w? X m8 Q \Q 5vllrlwazzzzzfarz fi FI/IIIIL l// R fi g .3 R

m 3 3 IL m3 no Q INVENTORS.

W/LBUR I JESSUP GEORGE L. 6R0 V5 457% v7. 7. NW

ATTORNEYS- June 9, 1959 w. F. JESSUP ET AL 2,889,665

COMPENSATING DEVICE FOR GRINDING MACHINES Filed Oct. 7, 1957 4Sheets-Sheet 3 INVENTORS.

W/LBUR F. JESSUP GEORGE L GROVE ATTORNEYS.

States This invention relates to grinding machines and, moreparticularly, to a device for automatically adjusting the position ofthe wheel head of a grinding machine to compensate for wear of thewheel.

The conventional grinding cycle of either centerless or center typegrinding machines generally consists of a rapid traverse movement of thewheel head toward the work to bring the wheel into grinding positionfollowed by a fast infeed movement of the wheel for coarse grinding ofthe work to approximately the finish diameter. At the end of the coarsegrinding operation the infeed is reduced to a slow feed rate for finishgrinding the work to final size after which the wheel head is retractedfrom the work. The point at which coarse grinding ends and finishgrinding begins is normally determined by a gauge which signals theapproach of the work to final size. When the work has reached its finaldiameter, the gauge provides another signal which stops the slow feedand initiates retraction of the wheel head from the work so as to permitloading of the next'piece to be ground. This grinding cycle is repeatedfor each successive piece of work with intermittent truing of thegrinding wheel to maintain a sharp and accurate cutting surface thereon.

As the grinding operation continues, the diameter of the grinding wheelbecomes progressively smaller due to attrition of the wheel caused bythe grinding and truing operations. Unless some means is provided tocompensate for this wear of the wheel, the fast feed rate portion 'ofthe infeed cycle will continually increase due to cutting of air as theface of the grinding wheel recedes further and further from the work.This is undesirable since it lengthens the time of the grinding cycleand reduces the production rate of the machine.

Means have heretofore been provided for automatically compensating forwheel wear, one such means being shown and described in the Decker andKearns Patent No. 2,641,876, patented June 16, 1953. The mechanism shownin this patent includes mechanical, electrical, and hydraulic componentswhich function to maintain the distance moved by the wheel duringinfeeding movement substantially constant despite the wear of the wheel.

It is an object of the present invention to provide a simple mechanicaldevice which will produce a compensation similar to that produced by themore complicated mechanism of the Decker et al. patent.

Another object of the invention is to provide a wear compensation devicefor a grinding machine which utilizes a one-way driving connection tomeasure the amount of wear of the wheel and to advance the wheel towardthe work by a corresponding amount.

With these and other objects in view, which will become apparent fromthe following description, the invention includes certain novel featuresof construction and combination of paits, the essential elements ofwhich are set forth in the appended claims, and a preferred form atentor embodiment of which will hereinafter be described with reference tothe drawings accompanying this application. In the drawings:

Patented June 9, 1959 2 Fig. 1 is a front view of a machine embodyingthe principles of the present invention.

Fig. 2 is a front elevation of a portion of the machine shown in Fig. 1with parts broken away to show the rela tion of the novel structure withthe prior art grinding machine.

Fig. 3 is a horizontal cross sectional view taken through the structureshown in Fig. 2. v

Fig. 4 is an end view taken along the line 44 in Fig. 3.

Fig. 5 is a hydraulic diagram which illustrates the operation of theinfeed mechanism of the present machine.

Fig. 6 is a wiring diagram which shows the electrical circuits employedfor controlling the infeed mechanism.

Fig. 7 is aschematic view illustrating one form of gauge which isadaptable for use with the present machine.

In the accompanying drawings, the invention is shown applied to acenterless grinder of the infeed type. It will be appreciated as thedescription proceeds, however, that the invention might equally well beapplied to a center type grinder such as that shown in the Decker et al.patent.'

As shown in Fig. l, the grinder is provided with a base 10 on which issupported a grinding wheel 11 for rotation about an axis which is fixedwith respect to the base 10. The work piece 12 to be ground is supportedon a work rest blade 13 and is pressed against the wheel 11 by a secondgrinding wheel 14 which rotates at a reduced speed and serves toregulate or control the rotation of the work piece 12 as it is beingground by. the wheel 11. The wheel 14 is carried by a wheelhead 15 whichis guided by ways 16 carried by a lower slide 17.

The lower slide is suitably guided for sliding movementi 'on the base 10and carries at its forward end the work rest blade 13 as illustrated inFig. 1. A clamp 18is provided for securing the wheelhead 15 to the lowerslide 17 so that the two will move as a unit on the base 10.

A second clamp 19 is provided for securing the lower slide to the basewhereupon the wheelhead may be traversed along the lower slide byreleasing the clamp 18.

For setup purposes, the wheelhead is provided with a hand wheel 20 whichis adapted to rotate a nut journaled in the wheelhead and meshing with afeed screw. This mechanism is fully explained and described in the Balland Grove Patent No. 2,709,877, issued June 7, 1955. In setting up themachine, the wheel head 15 is clamped to the lower slide 17 bytightening a clamping lever'18,

and clamp 19 is loosened to permit the lower slide to move with respectto the base 10. The handwheel 20 is then turned to feed the wheelhead 15and lower slide 17 as a unit along the bed until the work rest blade isbrought into proper position. The clamp 19 is then tightened, and theclamp sired setting of the wheel 14 independently of the work rest blade13. The clamp 21 (Fig. 1) is then tightened to clamp the nut withrespect to the wheelhead 15 as explained in the Ball et feeding movementof the rotation of the feed screw.

The present machine is desirably provided with the wheelhead to beeffected by these parts being similar to those bearing similar numbersin the last-mentioned patent. ever, that in the patent, the sleeve 34 ispinned to the feed screw 23, whereas in the present machine the sleeveis journaled for rotation on the feed screw by means of and a combinedradial and thrust,

a thrust bearing 35 hearing 36. These bearings are interposed betweenthe feed screw 23 and the sleeve 34 and are held in place between a nut18 loosened to permit the de-' al. patent to thereby enable.

It is to be noted, how-- 37 threaded on the feed screW- and -a shoulder38v suitably formed on the feed screw. As 'ex-' assaeezs 3 plained inthe'Stuc'key et al. patent, the walking beam operatesto bodilymove thefeed screw'in an axial direction to effect rapid traverse movement ofthe wheelhead and advance the grinding wheel 14 into grinding positionwith respectto the work.

, Inasmuch as in the present construction thefe'ed screw 23 is journaledfor rotation with respect 'to the walking beamf29, it is desirable forset-up'purposes to provide a clamp screw 39 '(Fig. 2) for preventingsuch relative rotation ofthe parts. For this purpose, the clamp screw 39is received ina tapped hole provided in the pivot pin 30 with the innerend of the screw adapted to bear against the feedscrew 23 and therebysecure the latter-against rotation when the clamp screw 39 is tightened.This will prevent rotation of the feed screw when the hand wheel 20 isturned to rotate the nut during the set-up of the machine. In thefollowing description, it will be assumed that the'machine has beenproperly set up and that the clamp screw 39 has been loosened so as topermit rotation of the feed screw. It will also be assumed that theclamp 21 (Fig. 1) has been tightened so as to prevent rotation of thenut in the cross slide whereby rotation of the feed screw will effectfeeding movement of the wheelhead.

, Secured to the right hand end of the base is a frame 45 which providessupport for the walking beam 29 and other parts of the infeed mechanismfor the grinding wheel 14. This frame is provided with an end cover orhousing '46 which serves to enclose the compensating mechanism whichforms the subject matter of the present invention. As shown in Fig. 2,the feed screw 23 is provided at its right hand end with an extension 47on which is mounted the automatic wear compensating mechanism 48 whichis more completely shown in Figs. 3 and 4. Fig. 3 also shows theprincipal elements of the walking beam type infeed mechanism which isfully disclosed in the Stuckey et al. patent but which will be brieflydescribed herein in order to provide a more complete understanding ofthe present invention.

The walking beam 29 is provided at each end with bi-.

furcations in which are slidably received blocks 49 and 50 which arepivotally supported by studs 51 and 52. The stud 52 is carried by apiston rod 53 which extends into a cylinder 54 formed in the frame 45.Secured to the piston rod is a piston 55 which works in the cylinder 54and which is adapted to be moved to the position shown in Fig. 3 whenhydraulic fluid under pressure is admitted to the cylinder through aport 56. Fluid is perrnittedto escape from the right hand end of thecylinder through a port 57. The piston 55 provides rapid traversemovement of the wheelhead toward the work by effecting axial movement ofthe feed screw 23 towardthe left as viewed in Fig. 3. When rapidtraverse movement of the wheelhead is desired, fluid under pressure isadmitted to the cylinder 54 through port 57 while port 56 is connectedto reservior. This will cause the piston 55 to move to the left end ofthe cylinder and cause the walking beam 29 to be rocked about the pivotpin 51. The walking beam will thereupon translate the shaft 23 towardthe left by means of pivot pins 30 and 31 (Fig. 2) which have theconnection previously described withthe feed screw 23. An adjustablestop screw 58 is threaded into atapped hole provided in the right handend cap of the cylinder 54 to establish the retracted position of. thewheelhead. Near the end of the rapid traverse movement of the wheelhead,a bracket 59 operates a lever 60 of a limit switch 2LS to initiatecoarse grinding ofthe work. While, in the present disclosure the bracket59 is shown secured to the piston rod 53, it will be appreciated that itmight equally well be attached to the walking beam 29 orformed as anintegral portion thereof. The

limit switch 2L8 is held in a fixed positon on the frame 45 by asuitablesupporting bracket.

a screw 66 meshing with a nut 67 which is fastened to the frame 45. Atits opposite end the feed shaft 65 passes through a bearing cap68 andhas journaled thereon a sleeve which carries the pivot stud 51.Intermediate its ends, the feed shaft 65 is provided with a key 69 whichslides in a keyway formed in a pinion gear 70 which is journaled forrotation in the frame 45 by antifriction bearings 71. Hence, when thegear 70 is rotated by means hereinafter to be described, the feed shaft65 will be rotated and the screw 66 meshing with nut 67 will cause theshaft to be advanced toward the left as viewed in Fig. 3. The rate atwhich the gear 70 is rotatedwill determine the fast or slow feed rate ofthe wheelhead toward the work. i

The portion of the hydraulic circuit of the grinding machine which ispertinent to the infeed mechanism heretofore described is shown in Fig.5 of the drawings. Fluid pressure for operating the system is providedby a hydraulic pump 75 which is driven by a suitable motor and delivershydraulic fluid under pressure from a reservoir 76 to a pressure line77. The pressure in the line 77 is maintained at a desired value by arelief valve 78 which returns excess fluid into the reservoir 76. Areturn line 79 empties into the reservoir 76 in a con ventional manner.Rapid traverse of the wheelhead is effected by energizing a solenoid1SOL whereby a spool 84 of a solenoid valve 85 is moved toward the rightagainst the force of a spring 86. Thereby hydraulic fluid connected byvalve 88 withthe reservoir line 79 so as to permit fluid in the lefthand end of the cylinder 54 to escape threefrom. Hence, the piston 55will be moved rapidly to the left as viewed in Fig. 5, thereby movingthe feed screw 23 to the left as viewed in Fig. 3. At the end of therapid traverse movement, the limit switch ZLS is operated, therebyenergizing a solenoid 2SOL (Fig. 5). This causes a spool 95 of asolenoid valve 96 to be moved toward the right against the urgency of aspring 97. Thereby, fluid under pressure from line 77 is deliveredthrough a line 98 to the right hand end of a control valve 99. Thisvalve contains a spool 100, which is thereby moved toward the leftagainst the urgency of a spring 101 so as to connect the pressure line77 with a line 102 connected to the left hand end of a cylinder 103containing a rack piston 104. The rack teeth on the piston mesh with theteeth of the gear 70 (see also Fig. 3). I

i the urgency of a spring 108 when a solenoid 3SOL is energized. Thisconnects line with a fast feed rate throttle valve 110, and thencethrough a check valve 111 and a line .112 back to the valve 99. In theoperated position of the valve 99 the line 112 is connected to thereservoir line.79, thereby permittingfluid to flow out of the right handend of cylinder 103 and through the throttle valve to reservoir. As thework approaches final size, a gauge hereinafter to be described providesa signal which deenergizes 3SOL, thereby blocking the flow of fluid fromline 105 through the fast feed rate throttle Coarse and fine grindingmovement of the wheelhead" is provided by a feed shaft 65 whichhas'secured thereto valve 110. The fluid flowing through line 105 isthereby constrained to pass through a slow feed rate throttle valve 113to line 112 and thence through valve 99 to the reservoir line 79. Thespeed at which the piston 104 moves ,toward the right as viewed in Fig.5 is thereby reduced so asto reduce the feed rate of the wheelheadproduced by the screw 66 (Fig. 3) and the feed shaft 65.

When the work reaches final size, the gauge provides a second signalwhich causes solenoids 1SOL and 2SOL to be deenergized. When 1SOL isdeenergized the solenoid valve 85 and control valve 88 return to thepositions shown in Fig. in which the motor line 92 is connected with thepressure line 77, and the motor line 91 is connected with the reservoirline 79. The piston 55 is thereby moved to its right hand position asdetermined by the setting of the adjusting screw 58. When solenoid 2SOLis deenergized, the solenoid valve 96 and control valve 99 return to thepositions shown in Fig. 5 wherein the motor line 102 is connected withthe reservoir line 79 while the motor line 112 is connected with thepressure line 77. Thereby fluid under pressure flows through a checkvalve 114 connected in parallel with the throttle valve 113 and throughline 105 into the right hand end of the cylinder 103. The rack piston104 is thereby rapidly returned to the position shown in Fig. 5 whichcorresponds to the retracted position of the wheelhead.

The gauge which provides the signals for controlling the infeedmechanism as the work is ground to size may be of the type shown in Fig.7 in which a feeler 120 turning on a shaft 121 is providedat its distalend with a finished surface 122 against which air from a nozzle 123 impinges. Thus, as the work 12 is ground to size, the flow of air throughorifice 123 is restricted by the approach of the surface 122, andsignals are provided which control the operation of the infeedmechanism. Provision may be made for moving the feeler 120 away from thework at the conclusion of the grinding cycle so that a new piece of workmay be placed in position for grinding. For this purpose, the feelercarries a gear 124 which meshes with a rack 125 which is normally heldelevated in the position shown in Fig. 7 by a tension spring 126stretched between a spring stud 127 on the rack and the shaft 121. Bylowering the rack 125 at the conclusion of the grinding cycle, thefeeler may be swung away fromthe work and from the nozzle 123 for theloading operation, after which it may be returned to the position shownin Fig. 7 by release of the rack 125.

'-'The gauge includes a pressure regulating valve 131 connected by aline 130 with a source of air under pressure. The valve 131 delivers airat constant pressure to a variable restriction or throttle valve 132.The delivery side of the valve 132 is connected by a line 133 and aflexible hose 134 with the orifice 123. Pressure in the line 133 iscommunicated to pneumatic relays 135 and 136 by lines 137 and 138. Therelays are also provided with a source of reference pressure deliveredthereto through a line 140 which is connected with the delivery side ofa pressure regulating valve 139 which has its input connected to thesupply pressure line 130. Pneumatic relays 135 and 136 are connected byair lines 141 and 142 with electric pressure switches 143 and 144 whichsignal the approach of the work to final size and also its arrival atthe finish diameter.

The specific manner in which the gauge controls the operation of theinfeed mechanism is shown by the wiring diagram in Fig. 6. Theelectrical circuit includes a pair of conductors 150 and 151 which areconnected by terminals 152 with a source of energizing current. Agrinding cycle is initiated by depression of a start push button 153(line 2) which energizes a control relay 3CR through a normally closedstop push button 154 and the normally closed contacts of a relay CR.When the relay 3CR is energized, the normally open contacts of thisrelay in line 3 are closed, thereby establishing a holding circuitaround the start push button 153 which maintains' the relay energized.At the same time, a pair of normally open contacts of the relay 3CR inline 4 are closed, thereby energizing the solenoid 1SOL (see also Fig.5) which operates valve 85 and initiates rapid traverse of the wheelheadtoward the work. At the conclusion of the rapid traverse movement, thelimit switch 2LS (line 5) closed, thereby energizing solenoid 2SOL (line5) which operates solenoid valve 96 and initiates operation of the rackpiston 104 (Fig. 5). Simultaneously, the solenoid 3SOL (line 7, Fig. 6)is energized through the normally closed contacts 155 of the electricpressure switch 143 (Fig. 7). Hence, the solenoid valve 106 is operated,thereby connecting the rapid feed rate throttle valve with the line 105so as to cause the wheelhead to be advanced toward the work at a fastfeed rate. At this time a signal light 159 (line 6) will be illuminatedso as to indicate that the machine is in the coarse grinding phase ofits cycle.

As the work 12 approaches its final diameter, restriction of the orifice123 (Fig. 7) increases the pressure in line 133 to the point where thepneumatic relay 135 operates the electric pressure switch 143, therebyopening the contacts 155 (line 7) and closing a set of normally opencontacts 156 (line 8). Thereupon, solenoid 3SOL will be deenergized,thus closing valve 106 and cutting 0E the flow of return fluid throughthe fast feed rate throttle valve 110. The fluid from the cylinder 103will now be forced to flow through the slow .feed rate throttle valve113, thereby reducing the infeed movement of the wheelhead to a feedrate suitable for finish grinding the workpiece. At the same time, asignal lamp 160 (line 8) will be illuminated to indicate a slow feedrate while the lamp 159 will be extinguished; When the diameter of thework has reached its finished size, the pressure in line 133 will besuch as to operate pneumatic relay 136 and the electric pressure switch144. This will cause the normally closed contacts 157 (line 9) of theswitch to open and the normally open contacts 158 (line 10) of theswitch to close. As shown in Fig. 6, the contacts 157 have no connectionin the electrical circuit while the contacts 158, when closed, energizea control relay 10CR, thereby opening the contacts of this relay in line2. The relay 3CR is thereby deenergized so as to open its contacts inline 4 and deenergize solenoid 1SOL.

The solenoid valve 35 (Fig. 5) thereby returns to the position shown inFig. 5- which causes the piston 55 to move to the right in cylinder 54and retract the wheelhead from the work. The opening of contacts 3CR inline 4 also deenergizes solenoid 2SOL thereby returning the rack piston104 to the position shown in Fig. 5. The lamp 160 will also beextinguished while a lamp 161 (line 11, Fig. 6) will be illuminated bythe closure of contacts 10CR in line 11, thereby signaling that the workpiece has been reduced to its finish diameter. The Work 12 is now readyto be ejected from the machine and a new piece of work loaded therein inpreparation for the next grinding operation. At this time the feeler isswung out of position by the rack (Fig. 7) so as to move the finishedsurface 122 away from the orifice 123. This causes the pressure in line133 to drop, thereby deactivating the pneumatic relays and 136. Thisreturns the electric pressure switches 143 and 144 to their normalpositions whereby contacts and 157 are again closed while contacts 156and 158 are again opened. Control relay 10CR is thereby deenergized toextinguish lamp 161 and again close contacts 10CR in line 2 ready forthe next operation. Since contacts 3CR in line 3 are now open, relay 3CRwill remain deenergized until the start push button 153 is againdepressed in order to initiate the next grinding cycle.

For the purpose of automatically adjusting the position of the wheel 14(Fig. l) to compensate for wear of the grinding wheel 11, the feed shaft65 (Fig. 3)'has secured to its right hand end a spur gear 165 whichmeshes with a corresponding gear 166 journaled for free rotation on theright hand end of extension 47 of feed screw 23 by ball bearings 167. Aportion of the teeth of gear 166 are removed to provide a seat for ablock 168 which is secured to the gear 166 and provided with aprojecting tooth or driver 169 as shown in Fig. 3. This tooth is adaptedto cooperate with a pair of abutment blocks 170 and 171 which areclamped by nuts 172 on tee bolts 173 7 to the periphery of an annularcontrol member 174. A portion of the periphery of member 17 4- isprovided with serrations 175 as shown in Fig. 4, which cooperate withcorresponding serrations provided on the underside of blocks 170 and 171to prevent slipping of the abutment blocks on the member 174. v t

The member 174 is fastened by a key 178 (Fig. 3) to a cam clutch 179having sprags 180 which provide a oneway driving connection between theshaft extension 47 and the'member 174. The member 174 and the cam clutch179 are retained on the end of shaft 147 by a nut 181 screwed on the endof shaft47 and a washer 182 When the wheelhead is in its retractedposition with the rack piston 164 (Fig. in its left hand position asshown in Fig. 5, the tooth 169 is adapted to engage with the block 170as shown in Fig. 4. However, during infeed movement of the wheelhead,the feed shaft 65 is rotated, thereby driving gear 166 through gear 165to move the tooth 169 in a clockwise direction as viewed in Fig. 4. Thetooth thereby leaves the block 170 and moves toward the block171.Theinitial setting of the block 171 on the member 174'as indicated bythe scale 185 (Fig. 4), which represents the travel of the tooth 169 interms of thousandths of an inch of movement of the wheelhead, is suchthat the tooth 169 will not quite contact the block 171 at the start ofthe grinding operation. However, as the grinding operation continues andthe wheel wears, the'infeeding movement ofthe whe elhead under thecontrol of the gauge will increase and the tooth 169 willfcontact theblock 171. When this occurs, the member 174 will be moved clockwise asviewed in Fig. 4' a slight amount, thereby causing slippage of the camclutch on the shaft extension 47. When the wheelhead 1s retracted at theend of the infeed cycle, the tooth 169 will return to the position shownin Fig. 4, However, since the member 174 has beendisplaced slightly in aclockwisedire'ction, the tooth 169 will contact the block 170 andreturnthe member 174 to the position shown in Fig. 4. Since this is in thedriving direction of the cam clutch 17 9, the shaft extension 47 andfeed screw 23 will be turned slightly in a'counterclockwi'se direction,thereby infeeding the wheelhead slightly toward the work. As the wheelcontinues to wear, this operation will be repeated, the amount of infeedmovement of the wheelhead provided by the feedscrew 23 being equal tothe Wheel wear. Hence, the in'feed movement of the'wheelhead provided bythe feed shaft 65 will always rem'ain the'same' regardless of wheel wearand the time of the grinding cycle'will remain constant. This will betrue regardless of whether the reduction in diameter of the grindingWheel is due'to the normal wheel wear or whether it results from atruing operation of the wheel. If the wheel is trued between grindingcycles, the control member 174 will beadvanced during the next grindingcycle by an amount equal to the amount of material removed from thewheel during the truing operation, and, atthe end of the infee'd cyclewhen the wheel head is retracted, the tooth 169 will engage the block170 and turn the member 174 and the feed screw' 23 by alike amount so'as.to infeed the wheel head by an amount equal to the stock removed fromthe wheel during the truing operation.

.While. we have described our invention in connection with one possibleform or embodiment thereof and have used, therefore, certain specificterms and language herein, it is to be understood that the presentdisclosure is illustrative rather than restrictive and that changes andmodifications may be resorted to without departing from the spirit ofthe invention or the scope of the claims which follow.

We claim:

1. In a precision grinding machine having a grinding" wheel carried by awheelhead supported for movenient toward andifrom a workpiece, thecombination of feeding means for inoving the wheelhead from a startingposition to an advanced position and back t'othe startingposition',-'"

means to stop the"- advance of the wheelhead by said feed: ing" meanswhen the workpiece reaches a predetermined siz e, and'rneans to-adjustthe feeding means to maintain successive strokes of the wheelheadsubstantially constant despite any reduction in the diameter of'thegrinding wheel, saidmeans including a rcciprocable driveroperativelyconnected-with saidgfeeding means for-movement in synchronism with theadvance and return strokes of the wheelhead, a driven member, a pair ofspaced abutments on said driven member disposed on opposite sides ofsaid driver, one of said abutments beingengageableby said driver neartheend of its advance stroke when such strokeis' greater than the previousadvance stroke thereof to move the driven member in one direction, andthe other of said abutments being engageable by said driver upon itsreturn stroke 'to return the driven member to its original starting;position, and a'one-way driving connection between said driven memberand said feeding means to permit free rotation of said member withrespect to said feedingrneans'in one direction of movement of saidmember, and to'cou'ple said member to said feeding means in the'otherdir'ection nf-movement of said member to adjust said feedingmeansandadvance the starting position of I thewheelha'd with respeot'to theworkpiece in-accordance member,- a pair of spaced abutments on saiddriven mem with the reduced diameter of the grinding wheel.

1 2. In a precision grinding machine having a grinding wheel carried by-a wheelhead supported for movement toward and from a workpiece," thecombination of feeding means for'moving the wheelhead from a startingposition to' fari advanced position and back to th'e'star'ting position,

means to stop the advance of the wheelhead bysaid feed-' ing means whentheworkpiece reaches a predetermined size, and means-'to'maintain'successive strokes of the wheelhead substantially constant despite anyreduction in the diameter of the grinding wheel, said means includingmeans toadju'st the starting position of said wheel'- head, a'reciprocable driver 'operatively connected with said feeding means formovement in synchronism with the advance and return strokes of thewheelhead, a-driven member, a pair of spaced abutments on said drivenmember disposedon opposite sides of said driver, onejof saidabutments'being engageable by said driver near the end or its advancestroke when'such stroke is greater than thepi-eviousadvance strokethereof to move the driven member i'n'one direction,- and the other ofsaid abutments being eh'gageable by said driver upon its return stroketo return the drivenmember'to'its original starting position, and aone-way driving connection between said driven member and said"adjusting means to permit the free rotation of said m'emberwith respectto said adjusting means in one direction of movement of said member, andto couple said member to said adjusting means in the other directionofmovement 'of said member to advance the starting position of thewheelhead with respect to the workpiece in accordancewith thereduceddiam'eter of the grindingwheel. 3. In a precision grindingmachine having a wheelhead supporting. a grinding wheeland a feed screwhaving a threaded connection with saidwheelhead for adjusting therelative position of the wheelheadwith respect to thefeed screw uponrotation of the latter, the combination of feeding meansfor bodilymoving said feed'screw intthe" direction of its axis from a fixedstarting position to an advanced position and back to its startingposition'toadvance'the wheelhead toward the work and retract ittherefrom, means for stopping the advance of the feed screwi by saidfeeding means when the workpiece reachesa predetermined size, andmeansto maintain successive strokes of the feed screw substantiallyconstantdespite any reduc-! tion in the diameter of the grinding wheel, saidmeans'includinga'recipro cable driver operatively connected with saidfeedingmeans for movement in synchronism with the advance andret'urnstrokes of the feed screw, a driven ber disposed on opposite sidesofsaid driver, one of said abutments being engageable by said driver nearthe end her to thereby rotate the screw and advance the starting of itsadvance stroke when such stroke is greater than position of thewheelhead toward the workpiece in accordthe previous advance strokethereof to move the driven ance with the reduced diameter of thegrinding wheel. member in one direction, and the other of said abutmentsbeing engageable by the driver upon its return stroke to 5 ReferencesCited in the file of this patent return the driven member to itsoriginal starting position,

and a one-way driving connection between said driven UNITED STATESPATENTS member and said feed screw to permit free rotation of 1,993,830Conover Mar. 12, 1935 said member with respect to said screw in said onedirec 2,049,611 Harrison et a1. Aug. 4, 1936 tion of movement of saidmember, and to couple said 10 2,518,600 Cox Aug. 15, 1950 member to saidscrew on return movement of the mem- 2,718,101 Stuckey Sept. 20, 1955

